BruceSteers said

If you've reversed the other list then it's index is just Length-position
same code as when i reversed the list and set the selected item.

ListBox2.Index = ListBox1.List.Max - ListBox1.Index

BruceSteers said

I had another idea…

To go backwards you could just take 10 from the index and then use the normal show 5.

Ie…

Code (gambas)

1. Public Sub btnBack_Click()
2.  
3.   ListBox1.Index = Max(0, ListBox1.index - 10)  ' go back 10 or to 0 if index - 10 is less than 0
4.  
5.   Button3_Click()  ' run the code that shows the next 5 items
6.  
7. End
8.